<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>

<body>
<div id="app">
    {{ msg }}
    {{age>18?"成年":"未成年"}}

</div>

</body>
<script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
<script>
    const app = new Vue({
        el: '#app',
        data: {
            "msg": "Hello World!",
            "age": 23
        }
    })
</script>
</html>